This invention relates to a hot water system having a provision for limiting heat loss from the hot water delivery pipes, and to a damped, gravity operated check valve for use in such a hot water system.
Prior practitioners in this area have concentrated upon designing hot water systems which would provide instantaneous hot water at a hot water discharge fixture such as a tap which is remote from the water heater location. Systems were designed to eliminate the inconvenience of having to wait for hot water to arrive at the tap while running the tepid water which had been standing in the pipes down the drain. These "instant" hot water systems such as those taught by U.S. Pat. Nos. 3,543,836; 3,556,124; and 3,929,153 employed various methods including hot water return lines, check valves, and even water coolers to ensure that hot water is instantly available at all hot water discharge fixtures within the system. Most of these "instant" hot water systems employed a technique of recirculating the partially cooled hot water which is in the delivery pipes back to the water heater to be reheated through a hot water return line. This approach necessitates the expense of installing additional piping from the most remote hot water fixture back to the water heater.
Of increasing concern currently is the energy cost required to reheat the recycled hot water. Considerable energy can be lost through heat which is radiated along the whole length of the hot water delivery pipe system and the hot water return line. Dramatic increases in energy costs within the past decade make this approach impractical, especially in residential or commercial installations where there are considerable periods during the middle of the day or at night when there will be little or no demand for instant hot water, yet water is being continually heated by the water heater and cooled in the delivery pipes. Consequently, what is needed today is a hot water system which will limit the amount of energy which is wasted through heat loss from the hot water pipes.
A conventional hot water system consisting of a water heater, delivery pipes and discharge fixtures without a hot water return line would lose less heat than would the aforementioned "instant" hot water systems, but would still lose a significant amount of thermal energy through heat radiation from the delivery pipes. Convection currents occurring within the delivery pipes would cause hot water from the water heater to migrate toward the cooler extremes of the delivery pipe network, particularly if the water heater is located below the delivery pipes such as in a basement. In such a configuration, the hotter water would tend to rise toward the delivery pipes in the upper floors, while the cooler water present in the delivery pipes would migrate downward toward the water heater. Thus as in the "instant" hot water system, heat energy is continually generated in the water heater and lost through the pipes, and once-heated water is cooled and reheated.
A check valve installed in the delivery pipe near the water heater would prevent such heat loss due to convection within the pipes. Gravity operated check valves such as those shown in U.S. Pat. Nos. 1,737,588; 1,913,622; 3,929,153; and 3,902,518 could be placed in the delivery pipes in such a way as to open when a discharge fixture is open and close when the discharge fixture is closed. However, the valves disclosed in the aforementioned references include no damping features and they would shut abruptly, causing noise and vibration in the delivery pipe system. This abrupt closure of the valve, in addition to its irritating noise, can have a detrimental effect on the plumbing system because of the resultant vibration.
Accordingly, what is needed is a hot water system that reduces the amount of energy lost through heat radiation from the delivery pipe network, operates automatically, and which does not cause irritating noise or harmful vibration.